The invention relates to a method for processing a slurry of coal particles in water. Aqueous coal slurries are obtained for instance in coal and brown coal mines, in the processing of coal (such as the deashing of coal or the dewatering of brown coal) and at the end of a pipeline in which the coal is transported as a slurry of powder or fines suspended in water. In most cases these coal slurries contain such a large quantity of water that as such they are unsuitable for use, for instance as a fuel. In many cases the coal slurries contain coal particles with a relatively continuous particle size distribution (e.g. of from 0 to 10 mm). Such slurries are often dynamically stable, which renders them suitable for pipeline transport, but statically unstable, so that they cannot be stored or transported by ship without the coal particles settling and the slurry becoming unpumpable.
Therefor, prior to use, storage or transport by ship such slurries have to be brought to a more usable form. To this end the coal slurry can in many cases be wholly or partly dewatered, so that a dry or wet solid cargo or a statically stable slurry is obtained.
However, a drawback of this direct dewatering is that it is very expensive, especially when the particle size distribution in the slurry is continuous. The whole slurry has then to be subjected to one or more treatments, which treatments are not always the optimum for all coal particles. When, for instance, a pipeline slurry has to be made suitable for transport by ship the following problems arise:
transport of the slurry itself by ship is not economical, in view of the high water content, while also segregation may occur, which will cause considerable problems when unloading the ship; PA1 mechanical dewatering of the slurry to an economically acceptable water content (for instance to a water content of 25 weight percent) yields a paste-like sticky mass which is very difficult to handle (no longer pumpable); PA1 continued thermal drying until a visually dry, solid cargo is obtained (having a water content of, for instance, less than 12 weight percent) gives a sufficient improvement in handleability but presents a dust problem, while, moreover, thermal drying of the whole cargo to such a water content is very expensive.
The present invention aims at solving these problems and providing a cheap, reliable alternative for processing such aqueous coal slurries.